Are You Confident of the Diagnosis?

What you should be alert for in the history

The diagnosis of trichofolliculoma is considered when a solitary slow-growing asymptomatic lesion appears on the face, neck, or scalp. Patients sometimes complain of thin hairs growing from the lesion and have cosmetic concerns associated with it.

Characteristic findings on physical examination

Trichofolliculoma is usually a single lesion that is found mainly on the face, but can be found on the scalp and the neck as well. It is usually of variable size ranging 2mm-1.8cm in diameter. It is a dome-shaped, pink-to-flesh-colored papule or nodule with defined margins. Sometimes, wool-like wisps of immature hairs can be seen emerging from a central orifice within the papule or nodule. It is not uncommon for the lesion to contain telengiectatic vessels (Figure 1).

Figure 1.

Solitary trichofolliculoma.

Sebaceous trichofolliculoma is a variant of trichofolliculoma that clinically presents as an ill-defined depressed lesion on the nose, with vellus and terminal hairs emerging from a sinus-like opening at the center of the lesion.

There have been several cases of eyelid trichofolliculoma, which are usually 2-3mm round pink papules with wool-like wisps of hair emerging from a central orifice.

Expected results of diagnostic studies

Three histologic stages of trichofolliculomas have been identified. These stages are divided into early, fully developed, and late stage.

Early-stage trichofolliculoma consists of a small superficial tumor. It is composed of several vellus hair follicles in anagen phase, leading to an infundibulum, which is slightly dilated, but not cystic. Single follicles do not end directly in the central infundibulum, but end in the adjacent epidermis.

Fully-developed stage trichofolliculomas demonstrate a central infundibular cyst with innumerable vellus follicles in anagen phase emanating from it. Sebaceous differentiation at this stage is absent. The perifollicular sheath is not thickened and the stroma is not as prominent as in late stage trichofolliculoma (Figure 2, Figure 3).

Figure 2.

Histopathology of trichofolliculoma at low magnification (H&E).

Figure 3.

Histopathology of trichofolliculoma at high magnification (H&E).

Late-stage trichofolliculoma consists of an infundibular cyst with less numerous, but more distorted, malformed vellus follicles. Sebaceous differentiation is present to a moderate extent, and is more pronounced compared to fully developed trichofolliculoma. In addition, the perifollicular sheath is thickened and sometimes has associated mucinosis and adipose tissue. A prominent stroma is present with many dilated vessels, numerous fibrocytes, as well as fibrillary bundles of collagen.

Histologically, the sebaceous trichofolliculoma variant shows abundant sebaceous acini associated with hair-bearing units, which are directly connected to the epithelial lining of the cavity. The classical trichofolliculoma does not have sebaceous acini associated with hair-bearing units. Sebaceous trichofolliculomas have been diagnosed using a radiopaque filling technique that reveals a well-defined shallow cystic space that is 2mm deep, without evidence of bone involvement.

The staining patterns on immunohistochemistry suggest that trichofolliculoma differentiates mainly toward the hair bulge and the outer root sheath in the isthmus. The following staining patterns have been observed in trichofolliculomas:

- Cytokeratin 14 was present in the entire layer of secondary follicles.

- Cytokeratin 15 was present in the outermost cells in epithelial strands in the secondary follicles (basal layers). It was present exclusively in the outermost cells in the hair bulge.

- Cytokeratin 16 was present in the innermost cells in the isthmus.

- Cytokeratin 17 was present in the suprabasal layers in the follicles, infrainfundibulum, and outer root sheath.

- Cytokeratin 1, 10, and 19 were not detected in trichofolliculoma.

Diagnosis confirmation

The differential diagnosis includes other follicular tumors such as trichoepithelioma and trichoadenoma. Trichofolliculomas can also resemble basal cell carcinoma.

Trichoadenomas are commonly placed in a spectrum of follicular neoplasms between trichoepithelioma and trichofolliculoma. Trichoadenoma expresses only cytokeratin 10 and 15, while trichofolliculoma does not express cytokeratin 10, but does express cytokeratin 15, 16, and 17. In addition, trichoepithelioma expresses only cytokeratin 15.

Basal cell carcinoma may appear similar clinically to trichofolliculoma, especially in the elderly; the two entities can be easily confused as both can be pink-flesh colored papules. However, they can be distinguished histologically. In addition, trichofolliculomas stain positive for CD34, while basal cell carcinoma stain negative for CD34.

Clinically, a hair follicle nevus can be confused with trichofolliculoma as well; however, both can be distinguished on histology.

Many believe that the folliculosebaceous cystic hamartoma is in fact a late-stage trichofolliculoma. The reason for this thought is mainly the histologic appearance of folliculosebaceous cystic hamartoma and late stage trichofolliculoma.

On histology, folliculosebaceous cystic hamartoma consists of an infundibular cystic structure connected to many sebaceous lobules. The epithelial structures are surrounded by a prominent stroma that is rich in blood vessels and fibrocytes. In addition, varying amounts of adipocytes are present in the stroma as well. All of these histological findings are similar to the histology seen with late-stage trichofolliculoma.

Who is at Risk for Developing this Disease?

While the exact incidence is unknown, trichofolliculomas are rare benign hamartomas. They may occur at any age and do not have specific predilection to either females or males.

In one study looking at fifteen patients with trichofolliculomas, the age ranged from 1-83 years, and the disease affected six males andnine females. In another study looking at thirty-one patients with trichofolliculomas, sixteen males and fifteen females were affected. There are no associated risk factors for developing trichofolliculomas.

What is the Cause of the Disease?

Etiology

Pathophysiology

The etiology of trichofolliculoma remains unclear.

Systemic Implications and Complications

Trichofolliculomas are benign hamartomas. Although there are no systemic implications or complications, trichofolliculomas may be cosmetically unappealing in some patients, and may be responsible for psychological concerns. Management of these concerns should be addressed on an individual basis.

Treatment Options

Treatment options are summarized in Table I.

Table I.

Treatment options for trichofolliculomas.

Medical Treatment

Surgical Procedures

Physical Modalities

Intralesional corticosteroids

Physical extraction

Laser Ablation

• Carbon dioxide laser alone

• Er:YAG (erbium:yttrium aluminum garnet) laser alone

• Combination of carbon dioxide and Er:YAG laser

Deep shave removal

Punch excision

Excisional surgery

Electrosurgery

Optimal Therapeutic Approach for this Disease

Initially, treatment should focus on reassuring the patient about the benign nature of the lesion. If the patient has cosmetic concerns associated with the tumor, treatment options are given.

Physical extraction of hair emanating from the lesions should be done with the awareness that plucking may cause inflammatory reactions.

Intralesional corticosteroids have been shown to decrease the size of the lesion. Corticosteroids can be used initially to shrink the size of the tumor, thereby decreasing the extent of scarring if surgical techniques are later pursued.

Complete excision is the ideal surgical option for definitive removal in patients with trichofolliculomas, if cosmetically appropriate. Trichofollicloma is commonly a solitary lesion, and basal cell carcinoma is an important differential diagnosis that needs to be ruled out.

Trichofolliculomas, like all adnexal tumors, can extend deep into the dermis, and the deeper dermal component is more likely cleared with a complete excision. If a complete excision is not possible, a deep shave of the lesion can be done, but it will not guarantee that the entire tumor is removed, and the patient should be counseled about the chance of recurrence. In addition, if the tumor is small, a punch excision around the visible tumor margins can be attempted. This method may reduce the chance of recurrence, and the defect size may be smaller than with a complete surgical excision.

Other modalities, such as carbon dioxide laser and Er:YAG (Erbium:yttrium aluminum garnet) laser, alone or in combination, can also be used. Laser surgery has been reported in other adnexal neoplasms, such as trichodiscomas and trichoepitheliomas, with success and good cosmetic outcomes.

Laser ablation provides good precision and has fewer thermal effects compared to electrocautery; however, recurrence has been reported in these cases. Because trichofolliculomas can extend into the dermis, trichofolliculomas treated with laser ablation have a potential to recur. If laser treatment is attempted with deeper and multiple passes, recurrence can be prevented, but there is an increased risk of scarring.

Electrosurgery can also be used, but hypopigmented scars may replace the lesions because of thermal effects. A limited depth of treatment with electrosurgery also increases the risk of recurrence.

Patient Management

Recurrence after complete surgical excision with negative margins is unlikely. If the diagnosis of trichofolliculoma is confirmed on biopsy, however, no further treatment or follow up is necessary.

Unusual Clinical Scenarios to Consider in Patient Management

An unusual presentation of trichofolliculoma in the vulva has been reported.

Collision tumor of trichofolliculoma and basal cell carcinoma has been identified in one rare case.

What is the Evidence?

(This was an article that detailed the different pathological stages of trichofolliculoma. It explained the difference in each stage: early stage, full developed stage, and late stage, and supplemented the explanations with many pictures.)

(This was a very detailed study with lots of informative pathology pictures of folliculosebaceous cystic hamartoma and late stage trichofolliculoma. It discussed, at length, the histological differences and similarities between the two clinical entities.)

(This study demonstrated that immunohistochemistry can be used to determine the different cytokeratin staining pattern observed in trichofolliculomas and trichoepitheliomas, which are common differential diagnosis for trichoadenoma.)

(This article presented a case of recurrent trichofolliculoma of the eyelid after several different treatments. It explained the failure of intralesional corticosteroids and explained the rationale for recommending surgical excision.)

(This was a rare report of collision tumor of trichofolliculoma and basal cell carcinoma. Since basal cell carcinoma is a differential diagnosis for trichofolliculoma, this article was very informative, detailing the difference between trichofolliculoma and basal cell carcinoma.)